A type of surge arrester which incorporates a failsafe shorting and grounding mechanism to deal with sustained overloads is described in U.S. Pat. No. 3,340,431. The assignee of that patent and of the instant application, TII Corporation, markets an embodiment of the patent as the widely used 300 Series Station Protector.
In recent years there has been a growing movement to provide even greater security against equipment damage and to that end, known gas tube station protectors have been connected in parallel with air gap protectors, e.g. of the carbon block type, or have been modified to include back-up air gaps; in the event the gas tube fails, the air gaps provide interim protection.
The known arrangements for achieving these features are burdened by one or more disadvantages involving relatively expensive components or expensive assembly procedures, or noise prone gap structures, or lack of integral design leaving the unit vulnerable to inadvertent omission of the back-up unit.